ARINC 629 is a relatively new aircraft communications bus used in the aerospace industry, and on, for example, the Boeing 777 aircraft (for a technical description of the ARINC 629 protocol see, for example, `ARINC 629 Specification--Multi-Transmitter Data Bus: Part I--Technical Description--Oct. 16, 1991; Part II--Applications Guide--Jan. 26, 1988`, and Boeing Document No. D227W003, `ARINC 629 Communication System Description Document--Rev. A` dated May 21, 1992). This communication system is a time-division multiplex system which includes multiple transmitters with broadcast-type, autonomous terminal access. It supports quasi-real time data communication between many terminals over a common single-channel transmission medium.
The users, various flight control computers, avionics control units, and many other line replaceable units (LRUs), communicate to the bus by using current mode coupling upon expiration of all three of its protocol timers. This method of restricting bus access ensures that only a single user transmits on the bus at any given time. All connected users listen to all the data transmitted on the bus and decode the first word of a transmitted wordstring to determine if the information contained therein is required by that specific user. If it is, the information is passed to the local addressable memory space where it is available to that control unit. If the data is not required by that specific user, it is ignored.
The assignee of the instant invention designs and manufactures the Main and Back-up Electric Power Generating Systems for the Boeing 777 aircraft. As such, the control units of these two systems utilize the ARINC 629 communication protocol and must interface with various other system on the aircraft (see FIG. 1) via two ARINC 629 buses. As would be expected, a high degree of development, verification, and qualification testing is required of such systems before being certified for flight by the various regulatory agencies around the world. Each and every aspect of the control, protection, power transfer, error detection, and communication functions of the control units must undergo rigorous testing under both normal and abnormal, emergency conditions. This testing includes the development and qualification, at both a LRU and system level, of the ARINC 629 communication. At this time, however, very little commercial ARINC 629 test equipment is available. Of the limited amount of equipment which is commercially available, none meets all of the assignee's line replaceable unit (LRU) and system test requirements.